The present invention relates to an adapter for a flow sensor used to detect a respiratory flow based on a differential pressure generated between both ends of a fluid-resistant member.
As a technique for detecting a respiratory flow based on a differential pressure generated between both ends of a fluid-resistant member, for example, Japanese Utility Model Publication No. 63-40967Y discloses, as shown in FIGS. 19A to 19C and FIG. 20, a sensor 100 for detecting a composition and a flow of respiratory gas based on a differential pressure generated between front and rear ends of fluid-resistant members 102 disposed within a tubular body 101 provided with pressure detecting passages 104, wherein each of the fluid-resistant members 102 has a shape symmetrical to a plane including a line A-A′ which is perpendicular to a gas flow and passing through windows 103 for measurement of CO2 concentration, and the fluid-resistant members 102 are symmetrically located in the tubular body 101. For this type of detection of respiratory flow, a gas to be measured is an inspiratory gas that is humidified by a humidifier or an expiratory gas that contains vapor, and vapor of the gas to be measured is accumulated in pressure detecting passages 104 or the like, which leads to the possibility that water drops fill the pressure detecting passages 104.
To avoid such possibility, a measuring system with a purge function that spouts out water drops filling pressure detecting passages is proposed to prevent measurement errors from occurring due to such filling (see U.S. Pat. No. 6,659,962). However, the purge function of this measuring system requires components such as a pump, a reservoir and the like, which may result in increase in size and costs of the system.
Further, it is proposed a device which includes a reservoir arranged within a tubular body and purges water pooled in the tubular body from the reservoir (see U.S. Pat. No. 4,932,269). However, this document does not provide any consideration of the possibility that water drops fill pressure detecting passages.
Moreover, tubes connected to the pressure detecting passages are attached to the tubular body in a radial direction thereof. This may cause the tubes to be kinked, thereby incorrect measurement would be caused.